U.S. President Barack Obama has thanked Congress for voting to help train and equip moderate Syrian rebels and expressed appreciation to France for offering to help in striking the Islamic State (IS) extremist group in Iraq.

Obama said France, "one of our oldest and closest allies," would be taking part in air strikes against "ISIL," an abbreviation for the group now commonly referred to as the Islamic State.

French President Francois Hollande's office said French jets on September 19 had carried out their first air strike against IS targets in Iraq.

Hollande's office said French jets had "completely destroyed" an IS logistics depot in northeastern Iraq. The statement said there would be further air strikes "in the coming days."

The AP news agency quotes Iraqi military spokesman Qassim al-Moussawi as saying four French air strikes hit the town of Zumar, killing dozens of militants.

Hollande said France won’t send ground troops and that France "will only intervene in Iraq" -- ruling out air strikes against IS targets in Syria.

France has already delivered arms shipments and humanitarian equipment to Iraq in the face of the IS extremist group's rapid advances.

Obama pointed out that France joined a growing coalition of countries in the fight against IS militants, saying, "more than 40 countries, including Arab nations, have now offered assistance as part of this coalition."

In his statement, Obama also thanked the U.S. Congress for approving a bill allowing U.S. military personnel to train and equip moderate Syrian rebel groups who are fighting both the troops loyal to Syrian President Bashar al-Assad and IS militants.

The Senate passed the bill on September 18 vote with 73 Senators in favor of the plan and 22 against.

The U.S. House of Representatives passed the bill on September 17.

"I'm pleased that Congress, a majority of Democrats and a majority of Republicans, in both the House and the Senate, have now voted to support a key element of our strategy – our plan to train and equip the opposition in Syria so they can help push back these terrorists," Obama said.

The bill grants authority for U.S. military personnel to train the selected Syrian rebel fighters at facilities in Saudi Arabia until the middle of December.

Obama said congressional backing showed IS militants that Americans are united in "confronting the threat from ISIL which has slaughtered so many innocent civilians."

Obama's statement also came after Australia conducted predawn raids in Sydney and Brisbane on September 18 aimed at countering a plot from IS supporters in Australia.

Fifteen people were detained. One of them has already been charged and ordered held until trial in November.

Prime Minister Tony Abbott said, "The exhortations, quite direct exhortations, were coming from an Australian who is apparently quite senior in ISIL (IS) to networks of support back in Australia to conduct demonstration killings here in this country."

According to Australian media, the plan involved snatching someone at random off the streets of Sydney and filming them being beheaded while draped in the black flag of the Islamic State.